1. Field of the Invention
The present disclosure relates to an electric power conversion apparatus, and more particularly, to the electric power conversion apparatus capable of determining a minimum output voltage of a boost converter for boosting a DC voltage to compare it with an input voltage of the converter, and controlling the operation of the converter based on the comparison result so as to reduce an unnecessary operation of the converter.
2. Description of the Related Art
The operation of a typical multi-string photovoltaic system is carried out by controlling a plurality of photovoltaic cell generators and converters connected thereto, respectively. The maximum power point tracking control of the generator should be always carried out to efficiently operate the multi-string photovoltaic system, and to this end, the converter is always controlled to output a constant high voltage.
FIG. 1 is a configuration diagram illustrating a multi-string photovoltaic system in the related art.
As illustrated in FIG. 1, in a multi-string photovoltaic system, a plurality of generators (that is solar cells) connect with DC/DC boost converters, respectively, to form parallel circuits.
The plurality of converters are connected to a DC-link stage, and a DC/AC inverter and an LC filter are provided therein, and a final stage thereof is connected to a grid, thereby configuring an electric power generation system.
Controller 1 recognizes the output voltage or current of the generator and operates the DC/DC boost converter to perform maximum power point tracking control. A DC-link voltage should be set to a constant high voltage to transfer an electric power generated from the generator to a grid, and it is set by controller 2 controlling the inverter. The controller 2 always controls the DC-link voltage which is an input voltage of the inverter with a constant high value, and due to this, the DC/DC boost converter is always operated to output a constant high voltage.
In the related art, the DC/DC boost converter is operated all the time, thus causing the switching loss of the converter as well as leading to a non-optimized efficiency of the overall system efficiency due to unnecessary electric power conversion.